The present invention relates to integrated circuits in general and, in particular, to voltage level shifter circuits.
Many electronics applications use voltage level shifting and driver components to handle high-side circuitry. Some of these applications provide a high-side switch, where a load is switched at the high side (e.g., the voltage supply side) of a circuit. For example, when a low-power voltage source (e.g., a computer output, battery, etc.) is used to drive a potentially high-current load, it may be desirable to provide a high-side switch that uses the low-power voltage source as a control signal to switch on another (e.g., higher-power) voltage source connected to the load.
Other applications may use level shifting and driver components to convert a direct current (“DC”) bus to an alternating current (“AC”) voltage for driving an AC system. For example, some uninterrupted power supplies convert a DC bus voltage to a three-phase waveform for power backup functionality, some motor controllers convert one or more DC bus voltages into two- or three-phase control signals, and some solar cells convert generated DC voltages into AC voltages for standard household uses. Certain other applications convert an AC voltage to a DC bus, which may then be used to generate a switched voltage signal of one or more frequencies. For example, when using a “Class D” audio amplifier to drive speakers, it may be desirable to increase the frequency of the amplifier, which may in turn decrease certain types of distortion (e.g., by effectively increasing the sampling rate).
Certain limitations of many voltage level shifting circuits, however, may prevent the reliable operation of these types of applications at high voltages and/or at high switching frequencies. One limitation is that the types of components in the circuit may generate excessive heat at high voltages and/or high switching frequencies, which may cause thermal run-away. Another limitation is that the configuration of components in the circuit may allow noise-induced cross conduction, which may short the DC bus voltage to ground. Either thermal run-away or shorting the DC bus to ground may, in some cases, cause permanent damage to the components and/or the packaging of the circuit.
As such, it may be desirable to provide voltage level shifting that may operate reliably and at low power, even at high voltages and high switching frequencies.